CMake: Force debug symbols on Linux

Fixes crash backtraces.

CMakeLists.txt

@@ -63,6 +63,14 @@ if(MSVC)
   set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} /OPT:REF /OPT:ICF")
   set(CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO} /OPT:REF /OPT:ICF")
   set(CMAKE_EXE_LINKER_FLAGS_DEVEL "${CMAKE_EXE_LINKER_FLAGS_DEVEL} /OPT:REF /OPT:ICF")
+else()
+  # Force debug symbols for Linux builds.
+  if (NOT CMAKE_C_FLAGS_RELEASE MATCHES "\\s*-g\\s*")
+    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -g")
+  endif()
+  if (NOT CMAKE_CXX_FLAGS_RELEASE MATCHES "\\s*-g\\s*")
+    set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -g")
+  endif()
 endif()
 
 # Warning disables.